In the field of power tools, and specifically in the field of battery-powered hand tools such as drills, one common type of motors used to provide the driving force is a self-contained “can-type” or “can” motor. They are permanent magnet DC motors and usually come with the armature wound on an iron core. Can motors typically include a housing in the form of a cylindrical can in which essentially all of the components of the motor are received, including the armature, magnets, brushes, motor housing, fan, and bearings. Most DC battery-powered tools incorporate a can motor to drive the power tool output due to the simplicity of assembly and low cost of can motors. Can motors are usually not designed to be disassembled and repaired. Rather, when a motor in a power tool burns out or wears out it is cheap enough to simply toss out and replace.
Another import type of DC motors commonly found in power tools are brushless motors. The brushless motor as its name suggests removes the need for commutators and brush assembly in the motor for creating alternating current to drive the motor. Rather, an electrical motor controller usually in the form of a semiconductor circuit or microcontroller takes the role to continually switch the phase to the windings in the motor stator to keep the motor turning. Brushless motors offer many advantages over brushed DC motors, including high torque to weight ratio, more torque per watt (increased efficiency), increased reliability, reduced noise, and longer lifetime.
However, most conventional brushless DC motors are made in the form of “open frame”, which means that there is no motor housing or “can” like that in can motors to enclose the brushless motor components. Instead, for open frame brushless motors used in power tools, the components of the motor are often installed in tool housings individually, and the tool housing incorporating open frame motors must be manufactured in factory prior to delivery to the user. As a result, the power tools once manufactured is then difficult to be repaired by the end user when there is a condition with the brushless motor, since the entire tool housing may have to be replaced in order to replace the old brushless motor.